1. Field of the Invention
The present invention relates to the preparation of cellulose films or fibers from cellulose solutions.
2. Description of the Prior Art
Cellulose for many years has been converted into fiber form using either the cuprammonium process or the viscose process, both of which involve derivatization and subsequent regeneration. The acceptance of rayon fibers has been limited because of the availability of inexpensive synthetic fibers prepared from petrochemicals. With the increased loss of crude oil renewed interest has been expressed in cellulose as a textile material. However, both of the commercial processes for preparing rayon fibers suffer from severe shortcomings. In particular, both processes are energy intensive, which to a large extent cancels out the potential savings obtainable from the use of cellulosic products as raw materials. Further, both the cuprammonium process and the viscose process produce effluent streams containing significant amounts of toxic materials which must be removed before the effluent can be disposed of. As a result, rayon consumption has not increased significantly. Cellulose fibers could supplant many of the synthetic fibers in textiles if they could be produced in a manner which is economically and environmentally superior to the techniques now available. This would reduce the consumption of non-renewable petrochemical resources.
The solubility of unmodified, that is nonderivatized, cellulose has been studied by many researchers. A review of the literature on these studies is found in Journal of Macromolecular Science--Review of Macromolecular Chemistry C 18 (1) (1980), Pp. 1-82, by Hudson and Cuculo. Scherer, in the Journal of the American Chemical Society, Vol. 53 (1931), Pp. 4009-4013, discloses dissolving cellulose in an ammonia-salt solution. However, Scherer's attempts to form films from the dissolved cellulose failed. Schleicher et al. in Faserforch Textiltech, 23, pp. 335-340 (1972), suggest dissolving wood pulp in a mixture of polar organic solvent, an amine and ammonia and a salt.
Accordingly, there exists a need for a process capable of producing cellulosic films or fibers economically and in an environmentally acceptable manner.